The present invention relates to a microwave oscillator, and more particularly to a transistorized microwave oscillator of the oscillation frequency multiplying type.
A typical transistorized microwave oscillator of the prior art is composed of a fundamental wave oscillator circuit involving a resonator and a frequency multiplier circuit for generating a required harmonic by multiplying the fundamental frequency of this oscillator circuit. Such an oscillator uses a frequency multiplier having a varactor diode for generating the required harmonic, requires a holding mechanism, a biasing circuit and the like for the diode, and accordingly has the disadvantages of complex structure and higher cost. Moreover, since the oscillator circuit and the multiplier are directly connected to each other, the load impedance of the former is the input impedance of the latter. Because of the consequent absence of buffering between them with respect to impedance fluctuations, any impedance fluctuation of the multiplier would become a load fluctuation of the oscillator circuit, resulting in the disadvantages that the start of oscillation is unreliable, and sometimes the oscillation even fails to start at all, furthermore frequency and output level fluctuations due to temperature variations are unstable, and abnormal oscillation is more likely to occur.